Electron tube apparatus



P 1957 B. c. GARDN ER ETAL 2,807,746

ELECTRON TUBE APPARATUS 5 Sheets-Sheet 2 Filed Feb. 23, 1954 552M420 0. G4 eon/5e 'MAEV/A/ C'noaoea w Passe-4 4 64 V4 E/A INVENTORS BY ATTORNEY Sept. 24, 1957 B. c. GARDNER ETAL ELECTRON TUBE APPARATUS 5 Sheets-Sheet 3 Filed Feb. 23, 1954 E'EAWAEDC. 614204152 MAM/w 000002010 f Puss/=2 z 6. #4214111 INVENTORS BY p 0 i ATTORNEY Sept. 24, 1957 B. c. GARDNER ETAL' 2,807,746

ELECTRON TUBE APPARATUS Filed Feb. 23, 1954 5 Sheets-Sheet 4 :EIIEI El EIE 11H FIE-1E IEI BEPUA ED 0. 6412041512 MAev/A/ C/voao/eow Passe-4 L fl. Mala/A IV INVENTORS ATTORNEY P 24, 1957 B. c. GARDNER ETAL 2,807,746

ELECTRON TUBE APPARATUS Filed Feb. 23, 1954 5 Sheets-Sheet 5 I hiy a a I 552M420 6! GA RDA/El? MAew/v C'HODOEOW 0 5624 M Mae/AN s INVENTORS A Troeuev United States Patent" 7, 2,807,746 Patented Sept. 24, 1957 nice 2,807,746 ELECTRON TUBE APFARATUS Bernard C. Gardner, Los Altos, Marvin Chodorow, Santa Qlara, and Russell H. Varian, Cupertino, Calif, assign'ors to Varian Associates, San Carlos, Calif, a corpora'tion of California Application February 23, 1954, Serial No. 411,623 14 Claims. (Cl. 315-551) This invention relates in general to electron tube apparatus and, more particularly, to improvements in klystron tubes of the floating drift tube type.

The floating drift tube klystron is similar toa two= resonator klystron in which the wall separating the two cavities is removed. The floating drift tube klystron is suitable for use as a generator of high frequencies and in this respect has characteristics similar to the reflex klystron. The advantage of the floating drift tube klystron is that it produces a high power output and efliciency substantially matching the two-resonator klystron while requiring only one tuning adjustment as in a reflex klystron. The floating drift tube klystron may be frequency modulated by applying a modulating voltage to the drift tube and may be amplitude modulated by use of a control grid to which the modulating voltage is applied. Or it may be modulated by use of a screen grid in front of the cathode and by applying a modulating voltage between the cathode and the anode.

One object of this invention is to provide a novel ultra high frequency generator of the floating drift tube type which will produce the high power and efliciency of the two-resonator klystron while utilizing the ease of tuning found in reflex klystrons.

Another object of this invention is to provide a floatingdrift tube oscillator which is rapidly tunable over a wide range of ultra high frequencies.

Another object of this invention is to provide a tunable ultra high frequency oscillator utilizing a novel noncontacting tuning plunger. 7 I

Still another object of this invention is to provide a novel tunable klystron of the floating drift tube type wherein the mechanical assembly used in controlling the tuner may be easily and rapidly removed from the tube body to enable utilization on other tubes.

Still another object of this invention is to provide a novel floating drift tube klystron wherein the drift tube is supported within the cavity resonator by a stern portion mounted in the side wall of the cavity, the stern portion being so arranged within the cavity so that parallel mode resonance is eliminated.

Still another object of this invention is to provide a novel floating drift tube klystron wherein the drift tube is supported by an integral member extending from the cavity resonator body, the member containing means for conducting a flow of fluid therein for cooling the drift tube.-

Still another object of this invention is to provide a novel klystron of the floating drift tube class having an improved cathode and associated modulating grid mounting' structure.

Other objects and advantages of this invention will be apparent from perusal of the following specification taken in connection with the accompanying drawings wherein one embodiment of the invention is depicted.

In the drawings,

Fig. 1 is a longitudinal section view of a floating drift tube klystronwhich embodies the present invention wherein the cathode assembly is shown in plan view,

Fig. 2 is a longitudinal section view of the cathode assembly,

Fig. 3 is a partial section view showing in clearer detail a portion of the cathode subassembly shown in Fig. 2,

Fig. 4 is an enlarged section view of the drift tube and mounting structure as seen looking down on it in Fig. 1,

Fig. 5 is an enlarged view of the cavity resonator structure and drift tube shown in Fig. 1,

Fig. 6 is a plan view of a portion of the cavity resonator structure and the drift tube structure looking from the top in Fig. 5 with the top and bottom plates or walls removed,

Fig. 7 is a plan view of thetube looking from the left-hand side in Fig. 1 and showing the focusing magnets mounted on the tube,

Fig. 8 is a section view of the tube taken along section lin'es 8-8 in Fig. 7 looking in the direction of the arrows,

Fig. 9 is a plan view of the floating drift tube klystron looking from the right-hand side in Fig. lv showing the focusing magnets mounted thereon,

Fig. 10 is an isometric view partly in section showing the water cooling structure of this floating drift tube klystron,

Fig. 11(a) is a diagrammatic illustration of the cavity resonator and associated drift tube showing the electric field lines with the tube operating in the series mode,

Fig. ll(b) shows the equivalent circuit diagram for the series mode operation of Fig. 11(11),

Fig. 12(a) is a diagrammatic illustration of the cavity resonator and associated drift tube showing. the electric field lines with the tube operating in the parallel mode, and

Fig. l-2(b) shows the equivalent circuit diagram for the parallel mode operation'of Fig. l2(a-).

Referring to the drawings, there is shown therein a novel floating drift tube klystron: for utilization as an ultra high frequency oscillator which is rapidly tunable over an extremely wide bandwidth, for example, of the order of 20% with the tube operatingat about 9 kilomegacycles. For clarity in describing the construction of this klystron, it may be thought of as being assembled from five subassemblies including first, a two-gap cavity resonator portion includingthe drift' tube; second, a cathode gun subassembly; third, a collector subassembly; fourth, a frequency tuner subassembly; and fifth, an output wave guide subassembly. In addition to these subassemblies which are combined to form the floating drift tube, there are also several additional components included to complete the tube such as the liquid cooling structure, the beamfocusing magnets and the tube mounting blocks.

The cavity resonator portion of this specific embodiment of the invention comprises four metallic parts of a highly conducting material, for example copper, including a body portion 1 of substantially a rectangular block configuration (Figs. 5 and 6) having a large bore 2 extending vertically therethrough and rectangular recesses 3 and 4 in the side wall thereof in which the tuning and outputwaveguide subassemblies are adapted to be mounted, respectively. A cylindrical drift tube 5 having tapered knife-edge ends and a two-step bore extending vertically therethrough is securely mounted as by brazing within one wallof the resonator body 1 by means of an integral stem or rod portion 6. The larger diameter portion of the bore in the drift tube is adjacent the input or buncher gap. In the present embodiment, the drift tube 5 and stem portion 6 are machined from one piece of metal.

7 The length of this stem must be properly chosen to pre- W vent resonance of this klystron in the parallel mode as will subsequently be explained. The stem portion 6 has a cylindrical bore or passage 7 therein for the purpose of water cooling as will hereinafter be described. A cylindrical tuner cooling orifice 8 (Fig. 10) is secured as by brazing within a small bore 8 in the cavity resonator block.

Mounted as by brazing in shallow circular recesses in the topand bottom of the resonator block 1 are the top and bottom plates or end walls 9 and 11. These top and bottom plates each have cylindrical portions protruding from the lower and upper surfaces thereof, the upper protruding portion 12 of the lower plate 11 and the lower protruding portion 13 of the upper plate 9 being tapered to knife-like edges, these edges combining with the tapered ends of the drift tube 5 to form the two resonator gaps. The top and bottom plates 9 and 11 have axially aligned bores therethrough which are also aligned with the bore in the drift tube.

' Mounted as by brazing on the under surface of the bottom plate 11 is an annular pole piece plate 14 of magnetic material having a substantially U-shaped cross section (see Figs. 1 and 2). The cathode gun assembly is secured to the under surface of this pole piece plate as by brazing with an annular separator 15 as of iron therebetween. An input pole piece 16 of steel having a hollow truncated cone shape is adapted to slip-fit over the circumferal edge of the pole piece plate 14, thispole piece 16 being secured as by brazing on a rectangular input mounting block 17 as of steel having a large cylindrical bore therein. Fitted within the large bore is a hollow cylindrical insulating tube 18 as of synthetic resin, this tube 18 beingheld in place by a retainer ring 19 of material similar to the insulating tube, the retainer ring being secured between the lower end of the mounting block 17 and the upper surface of a rectangular shaped metal base 21. The base 21 is secured by screws 22 to two rectangular mounting walls 23 and 24.

The cathode subassembly comprises an outer casing which includes a mounting cup 25, two substantially cylindrical hollow metallic seal tubes 26 and 27 and an end cup 28 along with two insulating cylindrical glass portions 29 and 31. Tube 26 has a groove encircling the outer surface thereof in which is located a coil of wire 32 which serves as a contact terminal for supplying negative potential to thecathode. Within this outer casing is the mounting structure for the cathode button, focus electrode and control grid which comprises a truncated cone 33 mounted at its base within the outer casing between the two seal tubes 26 and 27 by means of two annular metallic bushings 34 and 35. A hollow cylindrical metallic cathode support tube 36 is mounted at one end thereof in the smaller diameter end of the cone 33, the other end being flanged inwardly. Mounted on this flanged end of the support tube 36 is an annular cathode mounting member having a horizontally extending fiat portion or flange 37 and a vertically extending portion or flange 38 (Fig. 3). Secured as by spotwelding tovthe.

inner surface of the vertically extending portion 38 in spaced relationship are three multifolded cathode spacers 39 which are each made from a strip of metal such as tantalum. The cathode button 41 as of thoriated tungsten is mounted on these cathode spacers and held there by a clipping action between the ends of each spacer strip so asto be substantially axially aligned with the cathode support tube 36 and outer casing. Securely fixed on the upper side of the horizontal portion 37 of the cathode mounting member is an annular insulating member or spacer 42 as of ceramic. Mounted on the upper edge of this ceramic spacer 42 is a ring-shaped grid support or mounting member 43. Secured on this grid support is a fine mesh grid 44 as of tungsten which is concave shaped to conform to the emitter surface of the cathode button 41 and ispositioned so as to be properly spaced from the button forreasons subsequently explained. The grid 44 is secured on the grid support member 43 by means of a thin metal washer 45 as of tantalum. Mounted on the washer is a ring-shaped focus '4 member or electrode 46 and mounted on this focus electrode and extending downwardly over the cathode button mounting assembly is a cup-shaped shielding member 47 as of tantalum.

Extending through and sealed in the end cup 28 of the outer casing is a hollow cylindrical filament support tube 48, the inner end of the tube 48 having a second filament support or mounting tube 49 secured thereon and extending upwardly under the cathode button assembly. The lower end of filament support tube 48 which extends without the cathode casing is closed by a metallic cup 51 and associated glass seal 52. Extending through the cup in axial alignment with the support tube 48 and secured in the cup 51 as by brazing is a filament stem rod 53. Mounted on the inner end of this stem rod 53 as by connector strips 54 is one end of a filament wire 55 as of tungsten, the filament wire 55 extending upwardly under the cathode button 41 where it is wound in a noninductive spiral shape under the cathode button, the other end extending downwardly and being connected as by brazing to a terminal strip 56 which in turn is spotwelded to a tab protruding from the second filament support tube 49. A cup-shaped heat shield 57 is secured within the second filament tube 49 below the filament, this heat shield having an opening therein to permit the passage through of the filament wire ends. Secured over an opening in the end cup 28 of the cathode casing is a hollow cylindrical grid lead support tube 58 vacuum sealed at its outer end such as by a glass-to-mctal seal 59. Mounted in this seal 59 is a grid lead 61 which extends longitudinally through the cathode casing and through a small opening in the mounting cone 33, the inner end of this lead being brazed to a small grid connector lead 62 which in turn is secured to the grid support member 43. Also secured on the outer surface of the end cup 28 is a solid metallic cylindrical, ground connector 63.

Mounted as by brazing on the upper surface of the top plate 9 is a substantially cup-shaped output pole piece 64 of magnetic material having an opening in the lower end thereof through which the cylindrical protruding portion of the top plate 9 extends. The inner surface of this cup-shaped member has a two-step diameter into which is secured as by brazing a two-diameter cup-shaped collector adapter member 65. Secured within the smaller portion of this adapter member 65 is one end of a hollow 0 cylindrical collector tube 66 of good conducting material such as copper, the other end of this tube being closed by an end plug 67 of the same material. This collector tube 66 is axially aligned with the cathode subassembly, the drift tube, etc. and, with end plug 67, forms a part of the vacuum envelope of this klystron. Secured as by brazing within the larger diameter portion of the adapter member 65 is a hollow cylindrical tube or outer water jacket 68 of a water cooling system which is more clearly set out in Fig. 10 and will be fully explained subse quently.

The output waveguide subassembly comprises a rectangular waveguide portion 69 mounted at one end thereof as by brazing in one side of the resonator body 1, the

outer end having a waveguide window adapter 71 secured thereover. A waveguide flange 72 is secured on the win dow adapter, a glass or mica window 73 being sealed over the window opening in the flange 72. Extending through a wall into the waveguide portion 69 and brazed therein is a pinch-off tube 74 through which this floating drift tube is evacuated.

The tuner subassembly includes a hollow rectangular waveguide section 75 as of copper secured as by brazing at one end thereof in one side of the resonator block 1. The other end of this waveguide portion has mounted thereon as by brazing a thermal insulating member having a flanged circular base portion 76 and a rectangular protruding portion 77 which matches the rectangular end surface of the waveguide section 75. Mounted within the flange of the circular base portion 76 is an annular connector member 78 as of Monel. Secured to this con nector member as by brazing is a hollow cylindrical bellows joint 79 as of Monel to which is secured a metallic bellows 81 such as Monel, the other end of the bellows 81 being secured as by brazing to a bellows ring 82 as of copper. The tuner insulator 76, the connector member 78, the bellows joint 79, the bellows 81 and the bellows ring 82 are all axially aligned. 'Fixedly secured as by brazing to the bellows ring 82 is a hollow cylindrical plunger tube 83 which extends inwardly within the bellows 81. Secured within the inner end of the plunger tube 83 is a cone-shaped plunger 84. The elements 75 through 84 inclusive all form a part of the vacuum envelope of this tube.

Secured on the base of the cone-shaped plunger 84 is a substantially rectangular-shaped tuner plunger head 85 as of copper which extends axially through the rectangular openings in the connector member 78, the thermal insulator 76 and the waveguide section 75. The plunger head 85 has a wide groove 86 encircling a portion thereof and has the inner end thereof cut away to give a reduced rectangular portion. Secured on the inner end surface of this plunger head 85 is a U-shaped choke cap 87 of conducting metal such as copper, the legs of this cap extending back over the reduced end portion of the plunger head. Secured in the side surfaces of the plunger head 85 are a plurality of bearings 88 such as short cylinders of industrial sapphire which may be cut from bars of sapphire, these bearings serving as sliding contact points between the plunger head 85 and the waveguide section 75.

The cone-shaped plunger 84 has a threaded bore therein into which cap screw 89 is inserted to secure within the plunger tube 83 a cooler assembly which "comprises a cylindrical cooler tube 91 which fits snugly within the plunger tube 83, a substantially cylindrical cooler plug 92 having a cylindrical bore in one end thereof and a cone-shaped bore in the opposite end adapted to fit the cone-shaped plunger 84, and a cylindrical cooler sleeve 93 secured as by brazing within the cooler plug 92. These latter elements which are mounted on the plunger 84 by screw 89 are all outside of the vacuum envelope of the tube and, therefore, they and the subsequently described apparatus may be easily removed from the tube. The cooler plug 92 has a pair of grooves 94 (Fig. running longitudinally on the outer surface thereof positioned diametrically opposite each other, the two grooves being jointed by a circumferal groove 95 extending around the cooler plug near the inner end thereof.

Threaded into a bore in the cooler sleeve 93 is a tuner screw 96 which forms a part of the tuner shaft assembly. The tuner screw 96 is coupled by pins 97 to "a tuning shaft 98 having a knurled end which extends outwardly from the tuner subassembly. The tuning shaft 98 is mounted within a ball bearing 99 by means of a retainer ring 101. The ball bearing 99 is mounted within an axial bore in the end mounting flange 102 and held therein by an annular bearing cap 103 secured to the inside surface of the mounting flange 102 by means of screws 104. The end flange 102 is mounted in turn, as by screws 105, on a hollow cylindrical metal tuner shell 106 as of aluminum. The opposite end of this tuner shell 106 is secured within a circular opening in a rectangular mounting wall 23. This rectangular mounting wall 23 is in turn mounted on the output mounting block 107 and input mounting block 17 as by screws 108 and also is secured to the rectangular metal base 21 as by screws 22. The mounting wall 24 is also secured to the input mounting block 17 as by screws 108'. The mounting block 107 secures the output pole piece 64 within a bore thereof by means of set screws such as 109.

The heat generated by this tube is carried away by a. liquid cooling system, the coolant in the present fimbodl-i ment being water. The cooling system is set out in an isometric view in Fig. 10. The water input and outlet connection points are located in the cylindrical protruding "6 sides of acollector cooling head 111 which is mounted as by brazing on the cylindrical outer water jacket by means of an annular adapter 112. The water inlet is on the left hand side in Figs. 1 and 10. A portion of the water passes into a suitable conduit 113 as of copper tubing and the path of this water through the tube parts will be traced first. The piping passes through a bore 114 in the output mounting block 107 and into the cylindrical tuner cooler orifice 8 which is mounted in the cavity resonator block 1. The water passes into a bore in the orifice 8 where it cools the cavity resonator portion and then passes into additional piping 115 which leads into a cooling bellows 116 where a part of the heat from the water is dissipated in the air. The cooling bellows is designed to expand and contract as the tuner screw is turned in and out. The water then passes through additional tubing into one of the longitudinal grooves 94 in the cooler plug 92, the water passing down the groove and around the circumferal groove into the opposite longitudinal groove 94 where it then passes through tubing 117 into another cooling bellows 117'. The water is then passed into a bore in a cylindrical orifice 118 mounted onthe drift tube stem portion 6 (Fig. 4). The water passes into the bore 7 in the stem portion 6 and circulates toward the drift tube end where it then passes into the end of a hollow cylindrical tube or baflle 121 which is mounted at the other end in the bore of the orifice 118 by an annular baflle disc 122. The water passes out from the orifice into tubing 123 which extends through a bore in the output mounting block 107 and terminates in the output portion of the collector cooling head 111.

The remaining portion of incoming water passes within the outer water jacket 68 and down toward the collector cooler adapter 65 where it passes around the end of the hollow cylindrical inner jacket 124. This jacket 124 is secured at its upper end in the cooling head 111 and extends down over the collector tube 66, being spaced therefrom at all points by means of small indent portions 125. The water then passes up between the inner jacket and the collector tube 66 and then passes out through the output portion of the collector cooling head 111.

Referring to Figs. 7 and 9, the beam focusing magnets 127 and 128 are shown mounted on the tube stnucture by means of screws 129 threaded into the input mounting block 17 and the output mounting block 107.

In operation, electrons are emitted from the cathode button 41 and formed into a beam by the focusing electrode 46, the beam passing through the bore in the bottom plate 11. The beam passes across the lower or bun'cher gap formed between the plate 11 and lower edge of the drift tube 5 where velocity modulation of the beam is produced, the beam forming into bunches as it passes through the bore in the drift tube. The output resonator gap between the upper edge of the drift tube 5 (Figs.- 1 and 5) and the edge of the bore in the upper plate 9 extracts energy from the bunched beam and the tube is self-oscillating. The electrons then pass into the collector tube 66 and collect on the walls thereof. The frequency of oscillation is varied by changing the cavity size, using the plunger tuner mechanism 85, 87. The output energy is extracted through the output waveguide 69 and window 73.

The grid 44 is used to amplitude modulate the output of this floating drift tube klystron. The modulating signal voltage is impressed on the grid 44 to vary the beam current through the tube and thus effectively produce amplitude modulation.

In one floating drift tube made in accordance with the present invention, the tuning range of operation of the tube was 7.5 to 9.1 kilomegacycles. The tube was operated with the cavity resonator including the wall or electrode 11 grounded and with the cathode at a negative potential of 7 kilovolts. The grid was biased at a potential of 15 volts positive with respect to the cathode.

' The C. W. power output was about 500 watts,

Toprovide modulation of the output signal, themodulating signal was applied to the grid 44. In order to prevent defocusing of the beam due to the presence of this modulating voltage in the beam path, the grid 44 is carefully spaced from the cathode button emitter surface so that every point on the grid is located at or very close to a position in the space between the cathode and a positive electrode which coincides with the surface or zone of equipotential, which is present with the grid absent from the space, corresponding to the highest potential value reached by the modulating voltage which is to be applied to the grid 44. As known in the art, an equipotential surface is a surface all points of which are at the same potential in the electric field in the space between the cathode and the positive electrode or element. In the above described embodiment, the grid bias voltage was approximately volts positive with respect to the cathode and the modulating voltage swing positive on the grid was approximately 10 volts, therefore the grid was positioned as nearly coincident as possible with the equipotential surface in the space between the cathode button surface and the lower edge of the downwardly protruding portion of the wall or electrode 11 having a 25 volt positive potential with respect to the cathode. The modulating signal voltage on the grid thus swings about a value such that the maximum point of the modulating voltage coincides with the equipotential surface.

In constructing a floating drift tube of the type disclosed above, it was observed that, while tuning the tube over the range of operating frequencies, the power output dropped to a relatively small output at a certain band of frequencies and then increased again outside that certain band. The floating drift tube was being operated in the series mode and it was discovered that at that certain range of frequencies the interference in the power output was caused by the tube switching itsoperation from the series mode to the parallel mode. The series mode of operation is diagrammatically illustrated in Fig. 11(a) while the parallel mode of operation is illustrated in Fig. 12((1). In the series mode of operation the electric field exists across the two gaps in the same direction and thus the capacities thereof are in series. This is more easily seen in Fig. ll (b) which is the equivalent circuit diagram for the apparatus of Fig. ll(a). In the parallel mode of operation the electric fields across the input and output gaps are in different directions as shown in Fig. 12(a). The equivalent parallel circuit is shown in Fig. 12(b) where the inductance connected to the midpoint of the capacitors represents the drift tube support post.

It was discovered that this operation in the parallel mode within the voltage range of the desired frequencies was due to the dimensions of the drift tube support stem 6 which extended into the cavity from its mounting place in the side wall of the block 1. In order to prevent operation in the parallel mode within the operating range of the tube, it was necessary to change the dimension of the drift tube support stem 6 such as the length or diameter or both. In the present embodiment, the drift tube support was lengthened and mounted in a cut-away recess or alcove portion 126 in the cavity wall surface (Fig. 6) as this was the most suitable and expeditious manner of solving the problem. The parallel mode resonance could have been eliminated by changing the capacity of the resonator gaps but this would also have affected the operation of the tube in the series mode.

In the theory of a floating drift tube klystron of this type, for the greatest efficiency of MzVz M1V1 where M i=total effective beam coupling coefficient of gap 1 including gap spacing and diameter effects Mz=total effective beam coupling coefiicient of gap 2 including gap spacing and diameter effects V1=peak R. F. voltage at buncher gap V2=peak R. F. voltage at output gap.

Also for a very efficient tube MzV2+M1V1 should be about V0, the beam voltage, since a greater sum would turn back electrons. To obtain the condition one can modify the relative gap dimensions, that is, spacing and diameter of the output and input gaps. Making gap 1, the input gap, with a larger spacing than the output gap 2 will make Mz M1 due to gap spacing effects since larger spacing gives less effective voltage on the electron. However, since C1, the capacity of gap 1, is less than the capacity of C2 of gap 2 this will tend to make V1 Vz which will have the opposite effect on the above condition than the relative change of M2 and M1. Therefore while there will be some set of spacing dimensions which will optimize this ratio it does not allow unlimited variation because of the above noted cancelling effects. However, making the diameter in gap 1 larger than the diameter of gap 2 will make M2 Ml because of diameter effects; that is, for a given voltage between gap edges the effective voltage on the electrons decreases as the ratio of gap diameter to beam diameter is increased. This increase in diameter will also increase the capacity of gap 1 relative to the capacity of gap 2 and will therefore make V2 V1 and thus both of these effects aid each other. In one embodiment of this invention, the buncher gap spacing was approximately .050. The diameter of the drift tube bore at its input end was .128" while the diameter at the output end was .104".

Since many changes could be made in the above construction of the floating drift tube klystron and many apparently widely different embodiments of this invention could be made without departing from the scope thereof it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a high frequency device, a hollow cavity resonator body having a substantially cylindrical shaped side wall, the side wall having a recess formed in a portion thereof, said recess commencing at the inner surface of said side wall and extending outwardly from the cylindrical side wall surface, and a drift tube including a stem portion for suspending the drift tube in the cavity resonator, the stern portion being secured in said resonator body within the recessed portion thereof, said stern extending through said recess and into said cavity resonator, the length of said drift tube and stem construction measured from the axisof said drift tube to the mounting end of said stem being substantially longer than the radius of said cylindrical cavity whereby undesired modes of resonance are eliminated.

2. In a high frequency device, a cavity resonator portion comprising a hollow body having a side wall and end walls, said end walls each having an aperture therein,

a hollow member having open ends suspended within the cavity resonator with the ends aligned with the apertures in the end walls, the side wall of the cavity having a recess formed therein, said recess commencing at the inner surface of said side wall and extending outwardly from the side wall surface, and means for suspending the hollow member within the cavity resonator comprising a stern member mounted in the recessed portion, the stem extending through said recess and into said cavity resonator, the length of said hollow member and stem construction being substantially longer than the distance from said hollow member to said side wall whereby undesired modes of resonance are eliminated.

3. An electron discharge device of the floating drift tube type comprising a cavity resonator, a drift tube member including a stem portion having a passage extending therewithin, the drift tube being suspended within the cavity resonator by mounting the stem portion in the wall thereof, and means for circulating a coolant within the stem passage.

4. An electron dischargedevice of the floating drift tube type comprising a cavity resonator, a drift tube member including a stem portion, the drift tube being suspended within the cavity with the stem portion mounted in a wall of the cavity, the stem portion having a bore extending longitudinally therein, a hollow tube extending within the bore with its outer surface spaced from the wall of the bore, means coupled to thebore for passing liquid coolant into said bore between the stem portion and the tube and into the hollow tube, and means coupled to the tube for passing the liquid coolant out from the tube.

5. The combination, in an electron discharge device, comprising a support, an annular mounting member secured on the support, a cathode secured on the annular member within the central open portion thereof, an annular insulating member carried by the mounting member, a second annular mounting member secured on the insulating member with its central opening aligned with the central opening in the first mounting member, and a grid mounted on the second mounting member suspended in the central opening thereof spaced from the cathode.

6. The combination as claimed in claim 5, including an annular focusing member secured on the second mounting member in axial alignment therewith.

7. The combination, in an electron discharge device, comprising a hollow, substantially cylindrical support, an annular mounting member secured on one end of the support in axial alignment thereon, the mounting member having a first flange extending radially outward from the support and a second flange extending from the support parallel to the axis thereof, a cathode button mounted on the second flange within the central opening of the mounting member, an annular insulating member mounted on the radially extending flange, and a grid structure mounted on said insulating member and extending within the central opening thereof, the grid extending over the cathode and being uniformly spaced therefrom.

8. The combination, in an electron discharge device, comprising a base adapted to be mounted in an electron discharge device, a first mounting ring member fixedly secured on said base having a first flanged portion extending radially away from said ring member and a second flanged portion extending parallel to the axis of said ring member, a cathode button secured on said parallel extending flanged portion within the central opening of the ring member, an annular insulating member mounted on the radially extending flanged portion, a second mounting ring member secured on the annular insulating member, and a grid secured on the second mounting ring member over the central opening thereof and spaced from the cathode.

9. The combination for use in an electron discharge device comprising an outer casing which forms a part of the vacuum envelope of the device, a hollow truncated cone member mounted at its base end in the casing, a support member mounted in the other end of the cone, an annular mounting member secured on the support member, a cathode secured on the annular member within the central opening portion thereof, an annular insulating member mounted on the mounting member, a second annular mounting member secured on the insulating member with its central opening aligned with the central opening in the first mounting member, and a grid mounted on the second mounting member suspended in the central opening thereof spaced from the cathode.

10. A tuner structure for an evacuated electron discharge device comprising a waveguide mounted at one end on the device, a bellows secured at one of its ends on the other end of the waveguide, a hollow cylindrical plunger tube mounted on the other end of the bellows and extending inwardly into the bellows, a tuner plunger structure mounted on the inner end of the plunger tube having a plunger head portion extending within the waveguide, the waveguide, bellows, plunger tube and tuner plunger structure all comprising a part of the vacuum envelope of the electron discharge device, and an adjusting means coupled to the tuner plunger structure for adjustably moving the head portion within the waveguide.

11. A tuner structure as claimed in claim 10 including a plurality of sapphire bearings secured in the plunger head for bearing against the inner wall surfaces of the waveguide.

12. A tuner structure as claimed in claim 10 including a cylindrical cooler plug secured within the plunger tube having passages therein for conducting a cooling fluid whereby the tuner structure may be cooled.

13. In an electron discharge device, a collector assembly for collecting electrons comprising an annular cooler adapter, the central opening of which is aligned with the electron beam in the device, a hollow cylindrical outer tube secured at one end to the adapter, a hollow cylindrical collector tube positioned within the outer tube and secured at one end to the adapter and closed at its other end, the collector serving to collect the electrons in the beam, a hollow cylindrical tube jacket positioned between the outer tube and the collector tube and spaced from each, and means for passing a cooling fluid between the outer tube and the jacket and between the jacket and collector tube to thereby remove the heat generated in the collector by the electrons.

- 14. An electron discharge device of the floating drift tube type comprising a cavity resonator, a drift tube member, means for suspending the drift tube member within the cavity resonator including a stem portion coupled to said drift tube member having a passage extending therewithin, and means for circulating a coolant within the stem passage.

References Cited in the file of this patent UNITED STATES PATENTS 2,398,829 Heafi Apr. 23, 1946 2,405,175 Anderson et al Aug. 6, 1946 2,408,410 Clark Oct. 1, 1946 2,452,318 Nergaard Oct. 26, 1948 2,464,230 Harrison Mar. 15, 1949 2,466,704 Harrison Apr. 12, 1949 

